Lectin from inflorescences of ornamental crop Alpinia purpurata acts on immune cells to promote Th1 and Th17 responses, nitric oxide release, and lymphocyte activation.

Alpinia purpurata is an ornamental crop known as a source of bioactive molecules. This is the first study to report isolation of a lectin (carbohydrate-binding protein) from A. purpurata inflorescences (ApuL). The immunomodulatory potential of ApuL was evaluated by investigating its effects on the production of cytokines and release of nitric oxide by human peripheral blood mononuclear cells (PBMCs). In addition, the differentiation and activation of lymphocytes treated with ApuL was evaluated by immunophenotyping assays. ApuL is an acidic and oligomeric protein with native molecular mass of 34kDa. The hemagglutinating activity (HA) of ApuL was inhibited by the glycoproteins fetuin and ovalbumin, was resistant to heating at 100°C and stimulated in the presence of calcium and magnesium ions. ApuL showed highest HA at pH 7.5 but failed to agglutinate erythrocytes at pH 8.0 and 9.0. ApuL induced the release of cytokines belonging to Th1 (IFN-γ, TNF-α, and IL-6) and Th17 (IL-17A) profiles as well as of nitric oxide, stimulating a pro-inflammatory environment. Moreover, ApuL also stimulated the production of IL-10, an anti-inflammatory cytokine with regulatory role. Incubation with lectin resulted in differentiation and activation of both T CD8 ⁺ and CD4 ⁺ subsets of lymphocytes, as evident from the expression of the CD28 costimulatory molecule. In conclusion, A. purpurata inflorescence is a source of an immunomodulatory lectin with potential immunoregulatory application, thereby adding biotechnological value to this ornamental crop.
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